Mercaptothiazole

Alkylation of 5-mercaptothiazole in alkaline medium takes place on sulfur (348, 362). 

Many mercaptoazoles exist predominantly as thiones. This behavior is analogous to that of the corresponding hydroxyazoles (c/. Section 4.02.3.7). Thus oxazoline-, thiazoline- and imidazoline-2-thiones (521) all exist as such, as do compounds of type (522). However, again analogously to the corresponding hydroxyl derivatives, other mercaptoazoles exist as such. 5-Mercaptothiazoles and 5-mercapto-l,2,3-triazoles (523), for example, are true SH compounds. 

The thione form 202 is also characteristic of 2-mercaptobenzothiazole [76AHC(S1), p. 399], whereas the thiol tautomer was found to be the preferred form of 2-phenyl-5-mercaptothiazole 203 (76T583). 

This set of compounds is the most thoroughly studied among derivatives of 2-aminothiazole, thanks to the Beyer group. Heterocychzation methods are most commonly used for their preparation (see Chapter II and Refs. 37, 341, and 513-520). Reaction of 2-diazothiazoles (277) with organometallics provides another synthetic method (Scheme 1711 (521). 2-Hydrazinothiazoles may also be obtained by the action of hydrazine on 2-bromothiazoles (388) or on 2-mercaptothiazoles (522). 

Mercaptothiazoles. Hydroxythiazoles and their Derivatives II. 4- AND 5-SUBSHTUTED THIAZOLES... 

In the first chapter, devoted to thiazole itself, specific emphasis has been given to the structure and mechanistic aspects of the reactivity of the molecule most of the theoretical methods and physical techniques available to date have been applied in the study of thiazole and its derivatives, and the results are discussed in detail The chapter devoted to methods of synthesis is especially detailed and traces the way for the preparation of any monocyclic thiazole derivative. Three chapters concern the non-tautomeric functional derivatives, and two are devoted to amino-, hydroxy- and mercaptothiazoles these chapters constitute the core of the book. All discussion of chemical properties is complemented by tables in which all the known derivatives are inventoried and characterized by their usual physical properties. This information should be of particular value to organic chemists in identifying natural or Synthetic thiazoles. Two brief chapters concern mesoionic thiazoles and selenazoles. Finally, an important chapter is devoted to cyanine dyes derived from thiazolium salts, completing some classical reviews on the subject and discussing recent developments in the studies of the reaction mechanisms involved in their synthesis. 

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